#31: A Traffic Engineer and a TDM Planner Walk Into a Bar...

Author

Journey
August 14, 2025

Welcome to The Weekly Journey - your two-minute journey through the world of mobility and beyond. Use it to stay informed, find a new go-to source, or just have a peek inside how we think. Brought to you by the team at Journey.

A Journey insight. 💡

A Traffic Engineer and a TDM Planner Walk Into a Bar...

What happens when a traffic engineer and a transportation demand management (TDM) planner stop working in silos and start sharing a playbook?

At the 39th annual ACT International Conference in New Orleans last week, Journey TDM Lead Lauren Mattern joined Austin-based traffic engineer Bobak Tehrany, PE, of BOE to tell our story — how we bridged two disciplines that speak entirely different languages but shape the same streets.

The problem we kept running into:

  • Engineers are trained to move vehicles; TDM is about changing travel behavior. And their roles are siloed and unintegrated.

  • Traffic Impact Analyses (TIAs) rarely assume trips can actually be reduced.

  • Metrics like Level of Service (LOS) reward road widening, not trip elimination.

  • TDM is too often seen as a “nice to have” and not an integral part

The turning point:

In 2018, Bobak and Lauren met in Austin, introduced by local mobility leader Meg Merritt. Bobak was tired of measuring cars without changing outcomes; Lauren brought national TDM experience. Over coffee, they realized they could start inserting TDM into TIAs before anyone asked for it — and see what could happen.

It turned out the city was eager for it. Those early projects drafted the playbook and influenced what later became local standards. Developers and engineers began getting real numbers they could trust to quantify TDM outcomes.

Our playbook now looks something like this:

  • Frame TDM as risk management: Keep projects under traffic thresholds and avoid expensive mitigations.

  • Be the parking translator: Parking policy is the daily intersection of TDM and traffic engineering.

  • Speak their language: Translate TDM strategies into trip generation and other traffic metrics for credibility. 

  • Lock it into standards: Get mode-shift design elements written into engineering manuals.

  • Provide TDM inputs to models: Models only reflect the assumptions we give them.

What’s happened since:

Our developer TDM portfolio now sees up to 40% in parking reductions and 25% in trip reductions —meaning fewer cars on the road, smaller parking garages, and significant cost savings.

We are grateful to have found a traffic engineer who gets it — and we hope you find your counterpart too. The work gets a lot more interesting when we stop protecting our corners and start measuring success the same way.

A few interesting things. 🧠

🧑‍🤝‍🧑 Participatory Research: MassDOT, in partnership with the MassINC Polling Group and Way Finders CDC, just published a must read report focused on the transportation patterns, strategies, preferences of lower-income residents in Western MA. Make sure to check out the methods section.

🪙 Funding: The Build America Bureau just released a NOFO for the next round of the Innovative Finance and Asset Concession (IFAC) Grant program. Sign up for the free webinar.

🛣️ Long Commutes: A quick dive into changing commuting patterns in San Antonio (with some interesting comparisons to Austin).

📊 Service Planning, Airline Style: Airlines and transit agencies operate under very different constraints, but our team always appreciates network planning strategy whatever the mode. Check out this Cranky Flyer analysis of Alaska’s evolving approach.

Some fun job postings. 💪

A quick Journey update. 🏗️

👩‍🏫 Upcoming Events:

📚 Book Clubs:

  • ACT Book Club: Lauren hosts the monthly Association for Commuter Transportation Book Club. This month, the club is switching things up a bit and reading Supercommunicators by Charles Duhigg. TDM supercommunicator Jeffrey Tumlin will join the next meeting to share his insights and reflections. Sign up here to join us on August 27 at 3:00 PM Eastern / 12:00 PM Pacific.

  • Chicago City Builders Book Club: Lauren co-hosts the monthly Chicago City Builders Book Club - check out their new LinkedIn page to learn more. TONIGHT (August 14th) the group will meet up to discuss The Loop: The “L” Tracks That Shaped and Saved Chicago by Patrick T. Reardon. The author will join us and has challenged us to answer the question “how could Chicago be different if we never built the Loop?”

Journey Offices and DBE Certifications

Did someone forward you this newsletter? Be sure to subscribe to get The Weekly Journey in your inbox or follow us on LinkedIn.